Various security alarm devices are well known in the art. These devices sense various physical parameters in a space being monitored to detect unusual conditions indicating the presence of a potential alarm situation. There are many types of such devices, such as for example motion detectors based on detection of changes in infrared radiation patterns, motion detectors based on reflection of microwave or of ultrasonic signals transmitted into the space, vibration sensors, contact detectors, glassbreak detectors and so on. Some detectors combine different technologies into a single device.
Each of the devices in a security system is connected to communicate to an alarm panel. The panel monitors the status of all of the devices in the system and the system as a whole. When a valid alarm condition arises, the panel communicates same, usually by the public telephone system, to an outside agency such as the police or more commonly in recent years an alarm monitoring agency.
As is also well known in the art, many alarm devices, in addition to their primary sensing functions, have a tamper alarm associated with them. If a tamper sensor in the device (frequently, a tamper switch held in a normal position) is disturbed, the device reports an alarm condition to the panel.
It is desirable to test the proper operation of an alarm device when it is initially installed and, thereafter, on a regular basis.
Some alarm devices, e.g. passive infrared (PIR) motion detectors and microwave motion detectors, are quite directional in their coverage. A PIR detector, in particular, defines via its lens and sensor sub-systems a very specific coverage pattern in which there are multiple zones. Consequently, when detectors of this kind are installed, they should be properly aligned to provide the proper coverage in the premises to be protected. Subsequently, after installation, their continued proper alignment should be periodically checked.
The testing and checking of an alarm device is frequently done by means of a walk-test. To perform a walk-test, for example on a PIR motion detector, the person doing the test carefully walks through the space intended to be monitored by the detector. As he walks through the space, he watches for a detection response from the detector. Usually, the detector is provided with a small lamp, such as an LED, which lights when a detection has been sensed. In this manner, the person can assess whether the detector is identifying movement in the proper physical space where it is desired to detect such movement. If necessary, the detector can be adjusted or replaced to provide the correct coverage. As will be appreciated, a proper walk-test should be done carefully.
In a conventional hard-wired system, namely a system in which the various alarm devices draw their power from either the AC power lines or from a central power source, conserving energy at the device typically is not a primary consideration. Accordingly, in such systems, the walk-test indicator lamp can be permanently enabled, such that even when no specific walk-test is being done the walk-test lamp will light when a detection occurs. This means that, for example in an office setting, during the day as people walk by the detector, the walk-test lamp would be constantly turning on and off.
Such continuous detection activity would, however, represent an unnecessary energy drain on a battery-powered, wireless detection device. Accordingly, it is desirable in a wireless device to have all circuits active only when it is necessary for them to be active. This means enabling them and disabling them under the appropriate conditions or at the appropriate times. Thus, a walk-test circuit or lamp should only be enabled or engaged when it is necessary to perform a walk-test.
U.S. Pat. No. 5,499,012 discloses such a system in which operation of a tamper switch triggers enablement of the walk-test circuit and also operation of a timer. When a predetermined time is reached, the walk-test circuit is disabled. In other words, a limited period of time is available during which a walk-test can be performed. At the end of the pre-determined period, the ability to continue with a walk-test is terminated. To operate the tamper switch in the first place, it is usually necessary for the user to climb up (on a ladder, chair or the like) to reach the device because typically the alarm devices are often placed up high where they are not easily or accidentally disturbed.
The design disclosed in U.S. Pat. No. 5,499,012 can however be problematic. If the walk-test period is set too short and a walk-test has not been concluded when the timer times out, the user may simply not proceed further with the test because he would have to climb-up to the sensor a second time, operate the tamper switch again, and then proceed with the test, all of which may be inconvenient. The result would be an incomplete and unreliable test. Even if the user makes the effort to climb-up and operate the tamper switch again, in a second test, the positioning of the detector may have been disturbed or changed by the second operation of the tamper switch with the result that the second test may not quite match up or be aligned with the partial and incomplete first test. The continuity, reliability and thus results of the walk-test may therefore be suspect. Alternatively, if the user knows in advance that there is insufficient time for conducting a complete and careful proper walk-test, then he may be encouraged to perform the walk-test quickly with less precision and care than would be desired. The result in all such cases would be that the test may not be reliable.
On the other hand, if the walk-test period is set too long, then there may be many more detections than is necessary (for example, after the walk-test per se has been concluded, other people walk by the detector causing detections to be annunciated on the walk-test lamp) with attendant unnecessary energy drain on the battery.
In addition to the above, it will be appreciated, that different people will take different amounts of time to conduct a proper walk-test according to their personal preferences. As a result, it can be difficult or impossible to set a single pre-determined time which would be satisfactory to all users.